1. Field of the Invention
The present invention relates to a process for preparing a high-purity glyceride at a high yield in a short period of time.
2. Description of the Background Art
Glycerides are used as base materials in fields of cosmetics, drugs, etc., and as additives for improving plasticity of oils and fats and edible oils in a field of food. Such glycerides are generally prepared by an esterification reaction of glycerol with its corresponding fatty acid, an alcohol interchange reaction of glycerol with oil or fat, or the like. These preparation processes are roughly divided into chemical reaction processes, which make use of an alkali catalyst or the like, and biochemical reaction processes, which make use of a fat-hydrolyzing enzyme such as a lipase, or the like. However, the biochemical reaction processes are more generally used from the viewpoints of the yield and purity of the glycerides synthesized and the energy savings.
Conventional biochemical reaction processes include processes in which a fatty acid or the like is reacted with glycerol in the presence of a 1,3-position-selective lipase while removing water formed by the reaction outside the system, thereby obtaining a diglyceride at high yield and purity (Japanese Patent Application Laid-Open No. 71495/1989); processes in which glycerol is added in an equimolar amount or more to a fatty acid to react them, the reaction is stopped when the concentration of a diglyceride has been enhanced, insoluble glycerol is separated, and the reaction is further conducted while dehydrating, thereby synthesizing the diglyceride at a high esterification reaction rate by improving dehydration efficiency (Japanese Patent Application Laid-Open No. 330289/1992); and processes in which a mixture of a fatty acid or the like and glycerol or the like is reacted in a flow tube type reactor filled with a lipase while controlling the superficial velocity of the mixture in the reactor to at least 0.05 cm/s (Japanese Patent Application Laid-Open No. 234391/1998), etc.
Among the above-described processes, however, the technique described in Japanese Patent Application Laid-Open No. 71495/1989 does not investigate production conditions at an industrial level; the technique described in Japanese Patent Application Laid-Open No. 330289/1992 involves technical difficulties such as necessity of stopping the reaction at the time the concentration of the diglyceride reaches a peak; and the technique described in Japanese Patent Application Laid-Open No. 234391/1998 is easy to operate and can improve the reaction rate to some extent, but is insufficient in the purity of the resulting diglyceride and the industrial scale-up technique.
Accordingly, there is a need for a process for preparing a high-purity glyceride at a high yield in a short period of time at an industrial level.
It is thus an object of the present to provide a process for preparing a high-purity glyceride at a high yield in a short period of time at an industrial level.
This and other objects of the invention have been achieved by a process for preparing a diglyceride, which includes:
in an enzyme-packed tower which includes an immobilized lipase preparation, carrying out an esterification reaction between:
(1) an acyl group donor selected from the group including a fatty acid, a lower alcohol ester thereof, and a mixture thereof; and
(2) an acyl group acceptor selected from the group including glycerol, a monoglyceride, and a mixture thereof;
to obtain a reaction fluid from the enzyme-packed tower;
reducing a water content or a lower alcohol content in the reaction fluid; and
subsequent to the reducing, recirculating the reaction fluid to the enzyme-packed tower, wherein a residence time of the reaction fluid in the enzyme-packed tower is 120 seconds or less;
to obtain a diglyceride.
According to the present invention, a high-purity glyceride can be provided at a high yield in a short period of time.